To solve the problem, we will apply the principle of conservation of momentum. Let's break down the steps:
### Step 1: Understand the Initial Momentum
The initial momenta of the two balls are given as:
- \(\vec{p}_1 = p \hat{i}\)
- \(\vec{p}_2 = -p \hat{i}\)
The total initial momentum of the system is:
\[
\vec{p}_{\text{initial}} = \vec{p}_1 + \vec{p}_2 = p \hat{i} - p \hat{i} = 0
\]
### Step 2: Apply Conservation of Momentum
Since there are no external forces acting on the system, the total momentum before the collision must equal the total momentum after the collision:
\[
\vec{p}_{\text{final}} = \vec{p}_1' + \vec{p}_2' = 0
\]
### Step 3: Analyze the Final Momentum
From the conservation of momentum, we have:
\[
\vec{p}_1' + \vec{p}_2' = 0
\]
This implies:
\[
\vec{p}_1' = -\vec{p}_2'
\]
### Step 4: Evaluate the Options
Now, we will evaluate each option to see which ones are NOT allowed given that \(a_1, a_2, b_1, b_2, c_1, c_2\) are all non-zero.
#### Option 1:
\[
\vec{p}_1' + \vec{p}_2' = a_1 \hat{i} + a_2 \hat{i} + b_1 \hat{j} + b_2 \hat{j} + c_1 \hat{k} = 0
\]
This implies:
- \(a_1 + a_2 = 0\)
- \(b_1 + b_2 = 0\)
- \(c_1 = 0\)
Since \(c_1\) cannot be zero (given that all values are non-zero), **Option 1 is NOT allowed**.
#### Option 2:
\[
c_1 + c_2 = 0
\]
This allows for \(c_1 = -c_2\), which is possible even if both are non-zero. Thus, **Option 2 is allowed**.
#### Option 3:
\[
a_1 + a_2 + b_1 + b_2 + c_1 - c_2 = 0
\]
This can be satisfied even if \(a_1, a_2, b_1, b_2, c_1, c_2\) are all non-zero. Thus, **Option 3 is allowed**.
#### Option 4:
\[
a_1 + a_2 + b_1 + b_2 = 0
\]
Here, \(a_1 + a_2\) can be zero if \(a_1 = -a_2\) and \(b_1 + b_2\) can also be zero. However, since \(b_1\) and \(b_2\) cannot both be zero, **Option 4 is NOT allowed**.
### Conclusion
The options that are NOT allowed are:
- **Option 1**
- **Option 4**